To date solution rubber powders and their preparation have received comparatively little attention. This approach provides an economically attractive and advantageous procedure for preparing solution SBR powders and total powder blends thereof. This resulting total blended composition performs significantly, for example, in tire tread formulations and is one which is produced with a minimum of energy consumption and substantially reduced dust hazard in terms of both inhalation by workers and potential explosion hazard. A significant reduction in the amount of energy required is achieved and the final total composition, for example, results in excellent tire tread performance as evidenced in this specification. Hydrocarbon solution SBR powder compounds are directly processed, that is, without prior compacting or milling via, for example, a simple single screw rubber extruder with low L/D ratios.
Both the solution rubber powder and the total compounded composition produced as a result of this invention are free flowing and the requirement for substantial post blending shear is eliminated.
Utility for the totally compounded solution rubber powder blend is found in the production of, for example, injection molded articles, extruded exterior coatings in electric cable construction, tire construction, and, the preparation of gaskets for hose and pipe which can be utilized in both automotive and home construction.
Within the context of the present invention, the term hydrocarbon rubber solution describes hydrocarbon solutions of non polar rubbers, especially those which have been prepared by solution polymerization; examples thereof include solution SBR, solution polybutadiene, solution EPDM and solution EP. The viscosities of said rubbers are not critical to their performance in the practice of this invention; they can be either high or low. For example, the DSV's and ML.sub.4.sbsb.1.sbsb.0.sbsb.0 .sbsb.c of any such rubber can be between 1.5-7.0 and 20-180, respectively. DSV is defined as dilute solution viscosity and ML.sub.4.sbsb.1.sbsb.0.sbsb.0 .sbsb.c is defined by Mooney viscosity. Both methods are related to the molecular weight of the rubbers and are commonly used in the art for designating the molecular weight or viscosity of rubbery materials. The Mooney measurement is the most convenient measurement for the range of about 20-180, while the DSV measurement is more applicable for very low and very high viscosity elastomers; the preferred range is from 35 to 110.
Below 1.5 DSV, minimal rubber properties are evidenced and as the DSV increases up to 7.0 DSV, the higher viscosity increases reflect increased difficulty in processing; the preferred DSV range is from 1.8 to 3.0 as a result of which rubbery properties in the product and processing are optimized.